Chapter 3 Photorefractive Limits; Chapter 4 Cleaning And Maintenance; Cleaning The Optics; Cleaning The Compensator Housing - THORLABS EO-AM-NR-C Series User Manual

Chapter 3
Lithium Niobate, LiNbO
3
power densities up to 1 MW/cm
lead to color center formation and progressively increasing absorption. Photorefractive damage is noted by
increase scattering and absorption in the optical path along with gray appearance in the crystal (gray tracking).
Photorefractive limits are a concern in the visible region (400 – 700 nm) particularly with frequency- doubled
lasers.
The lithium niobate crystals in Thorlabs' EO modulators are MgO-doped for increased resistance to
photorefractive damage.
Chapter 4
Under normal operating conditions, the modulator needs very little, if any maintenance.

4.1. Cleaning the Optics

The modulator crystal is recessed inside the housing and under normal conditions, the crystal faces should not
need cleaning. If necessary, use a gentle stream of compressed air (dry nitrogen under low pressure or a can of
compressed air made specifically for cleaning optics).
Damage may result from excessive cleaning air pressure of if condensation is allowed to build up from using a stream of

4.2. Cleaning the Compensator Housing

The housing can be wiped clean with a lint free rag wetted with propanol or a commercial window cleaner. Do not
soak the housing – it is not watertight and any moisture introduced inside the modulator may cause condensation
problems.
Photorefractive Limits
, has an optical transparency range from 320 nm to over 5 µm and can withstand pulsed
2
. However, short wavelength operation is limited by photorefractive effects which
Cleaning and Maintenance
compressed air from an inverted can.
WARNING
Chapter 3: Photorefractive Limits
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